Existentialism and epistemology.

Comments on B. Vandenberg's (see record 1992-12211-001) article on epistemology and an existential consideration of development, taking exception with both his definition of existentialism and his characterization of Piaget's work. Existentialism, it is argued, is not an alternative to epistemology, but a particular style of responding to philosophic questions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A review of contractor selection practice in the U.K. construction industry

Background, prime influences upon present day methods and current trends in United Kingdom tendering practices are reviewed. Significant weaknesses are identified, confirming the need for some revision of existing contractor selection methods. The findings compliment recommendations of the recent government/industry review of the construction sector headed by Sir Michael Latham. Specifically, that tendering procedure should embrace investigation of contractors' potential to deliver a service of acceptable standard, on time, within budget. Present selection methods often fail in this objective, being inclined to discriminate predominantly on cost.     

PRMT 3, a type I protein arginine N-methyltransferase that differs from PRMT1 in its oligomerization, subcellular localization, substrate specificity, and regulation

Methylation is one of the many post-translational modifications that modulate protein function. Although asymmetric NG,NG-dimethylation of arginine residues in glycine-arginine-rich domains of eucaryotic proteins, catalyzed by type I protein arginine N-methyltransferases (PRMT), has been known for some time, members of this enzyme class have only recently been cloned. The first example of this type of enzyme, designated PRMT1, cloned because of its ability to interact with the mammalian TIS21 immediate-early protein, was then shown to have protein arginine methyltransferase activity. We have now isolated rat and human cDNA orthologues that encode proteins with substantial sequence similarity to PRMT1. A recombinant glutathione S-transferase (GST) fusion product of this new rat protein, named PRMT3, asymmetrically dimethylates arginine residues present both in the designed substrate GST-GAR and in substrate proteins present in hypomethylated extracts of a yeast rmt1 mutant that lacks type I arginine methyltransferase activity; PRMT3 is thus a functional type I protein arginine N-methyltransferase. However, rat PRMT1 and PRMT3 glutathione S-transferase fusion proteins have distinct enzyme specificities for substrates present in both hypomethylated rmt1 yeast extract and hypomethylated RAT1 embryo cell extract. TIS21 protein modulates the enzymatic activity of recombinant GST-PRMT1 fusion protein but not the activity of GST-PRMT3. Western blot analysis of gel filtration fractions suggests that PRMT3 is present as a monomer in RAT1 cell extracts. In contrast, PRMT1 is present in an oligomeric complex. Immunofluorescence analysis localized PRMT1 predominantly to the nucleus of RAT1 cells. In contrast, PRMT3 is predominantly cytoplasmic.     

Fast full‐color reflective display via photoluminescent enhancement

Reflective displays are advantageous in applications requiring low power or daylight readability. However, there are no low‐cost reflective technologies capable of displaying bright colors. By employing photoluminescence to more efficiently use ambient light, we created a prototype display that provides bright, full color in a simple, low‐cost architecture. This prototype includes a novel electrokinetic shutter, a layer that incorporates patterned luminescent red, green, and blue sub‐pixel elements, and a novel optical out‐coupling scheme. The luminescent elements convert otherwise‐wasted portions of the incident spectrum to light in the desired color band, resulting in improved color saturation and lightness. This prototype provides a color gamut that is superior to competing reflective display technologies that utilize color filters in single‐layer side‐by‐side sub‐pixel architectures. The current prototype is capable of switching in <0.5 s; future displays based on an alternative electro‐optic shutter technology should achieve video rate operation. A transflective version of this technology has also been prototyped. The transflective version utilizes its backlight with a power efficiency that is at least three times that of a conventional liquid crystal display. These photoluminescence‐based technologies enable a host of applications ranging from low‐power mobile products and retail pricing signage to daylight readable signage for outdoor advertising segments.     

Computer simulations of time-dependent suppression of EOF by polymer coatings

We use molecular dynamics simulations in order to investigate the time evolution of the effect of adsorbed polymer coatings on the electro-osmotic flow (EOF) in a capillary. Weakly adsorbed coatings show no time-dependent performance, but they do not strongly reduce the EOF. On the other hand, strongly adsorbed coatings made of longer polymer chains are often quenched in non-equilibrium conformations that can strongly reduce the EOF over extremely long periods of time. For intermediate adsorption strengths, we observe that the EOF increases as a function of time due to the relaxation of the coating layer. The concentration of polymers in solution and the length of the polymer chains also affect the time-dependence of the EOF. These results show that the quality of electrophoretic separations can depend on the waiting time between the formation of the coating and the beginning of the separation. We conclude by suggesting experimental tests of our predictions.     

Vortex rings and the superfluid λ-transition

A vortex-ring formulation of the₄He -transition provides a clear physical picture of the superfluid transition. The thermally excited rings are dipoles which orient in an applied flow field, and their net backflow cancels part of the applied flow, reducing the superfluid density. At the -point rings of infinite size drive the superfluid density to zero as a power law of the reduced temperature, with an exponent of 0.672. By fitting to the experimental superfluid amplitude the core energy of the smallest rings is found to be 6.1K at T and their diameter is 2.3 Å. It is proposed that these can be identified as the roton excitations of the Landau model. The vortex theory also yields new insights into topics such as boundary effects at a wall, finite-size effects, and the dynamics of the transition.     

Steric stabilization of Stöber silica dispersions using organosilanes

Organosilanes of the general formula R _x Si(OR)_4–x (where R is an alkyl group and R = CH₃ or CH₂CH₃) were used to sterically stabilize hexane dispersions of submicrometre silica spheres. The dispersions were characterized according to sediment volume results. For 0.5m silica particles, the sediment density increased by more than a factor of three up to 50 to 55% of theoretical in the presence of organosilanes with 12 or more carbons in the R group. Solid-state¹³C nuclear magnetic resonance was used to characterize the powder-dispersant interaction; this technique can distinguish between carbons in the R group of the organosilane and residual organic groups in the silica. Scanning electron micrographs of filter compacts were used to further characterize the dispersions and indicated the presence of primary particles as well as small agglomerates.